Fluid level system for circuit breakers



Feb. 9, 1932. l

J. D. HILLIARD FLUID LEVEL sYs'IEM Fon CIRCUIT BREAKERS John D. Hilliard,

ww/ His Abtorheg.

' source of danger place through conduit 19 into the.l interior of Since in operation the gas or air-contain:

ing space in the upper part of the switch housing should not be less than a certain minimum value, depending upon the particular construction of the circuit breaker, and the power interrupting capacity of the switch, a very large air space, in the event that no liquid level, regulating means are provided,

must be used in order that uctuations in the oil level due to the relatively large' coeicient of expansion of oil, may not reduce the air space below its required minimum, or expose thelower ends of the ground shields upon contraction of the oil body. rlhis problem is very readily understood when it is realized that the coeiiicient of expansion of oil is approximately 115 of 1 percent of its volume for each degree centigrade. A Y

Upon interruption of large currents, the gases formed by the power arc tend to move a'portion of the oil bodyv with great velocity vtowards the top of the circuit breaker, and

to create very high internal pressures therein.V

The air s ace beneath the cover 2 accordingly acts as a lider, or cushioning means. When.

the cushioning eect of the air space is reduced below a certain point, the internal pressures so set up within the circuit breaker are abnormallyhi h and may result in considerable damage-t ereto.

Considering now the existence ofan abnormally low oil level, as where the level is below the lower ends of round shields 4, a further dgue to secondary explosions within the switch housing is encountered. In other words, when the ground shields are out of contact with the oil, there is possibility of static arcing with the resultant i ition of thel highly iniiammable gases which generally collect within the air space, particularly immediately after interruption of the circuit. Obviously, such secondary explosions may be of such violent nature that considerable damage to the equipment in question may result. j v

By my invention, provision is ade for maintaining the level of the oil body substantially constant, whereby the lower ends of the ground shields may at all'times be sub-v merged in the oil, and wherein the air space need not be of excessive size, notwithstanding the tendency for large iluctuations in volume of the oil within the switch housing for any reasons whatsoever.

To this end, the overiiow conduit 9 discharges into the reservoir 11 upon rise of the Lacasse oil level beyond the (position illustratedin i Fig. 1. The restricte opening or vent 10 in the lower end of the discharge conduit prevents sudden expulsion of oil into reservoir 11 upon interruption of the circuit. Motor 13, which may be run either continuousl or at the will of the operator, actuates the uid impeller 15 to force oil from the reservoir by way of conduit 16, sight gauge 18 and conduit 19, back into the switch housing.r Accordingly, a continuous circulation ma be eected to maintain the oil level substantially constant. f

Assuming for the purpose of example, that vthe oil body contracts in volume dueto low temperature, the oil level will drop below the opening of the discharge conduit 9, so that reservoir 11 does not receive oil from the main body. However, due to the storage capacity of the reservoir, the iuid impeller will act to force oil through conduit 16, etc., back into the switch housing to raise the level a ain up to the discharge conduit opening. pon increase in tem above the opening of discharge conduit 9, thereby permitting ow of excess oil into reservoir 11. The storage capacity of reser; voii` 11 is such that its oil level will not fall below a certain minimum, as 11a, for extreme low temperatures, nor will it exceeda maximum level, as 11b, at comparatively high temperatures. Accordingly, it will be noted that the variations in volume of the oil body occur within reservoir 11, thereby maintaining the volume in the main switch housing substantially constant. v

' It should benoted at this oint that both the discharge and return con uits are located rature, the oil level rises` in proximity to the normal oil level. This body. Due to the fact that sludge or other sedimentary matterrequently accumulates in the bottom of the'switch housing, it is obvious that currents of oil near the lower part of the4 switch housing might stir up this sludge to cause it to mix with the rest of the oil body. Such disturbance' of the sludge is obviously objectionable and should be avoided. l

Referring to Fig.l 2, there is shown a modified form of the above described system wherein a circuit breaker similar to the vone previously described is provided with means for regulating the oil level in response to variations thereof. vTo'this end, a chamber 21 communicating by way of vent 22 with the interior 'of the switch housing 1, and mounted exteriorly of the housing is provided with'a float member 23 having an operating stem 24 extending through a conduit 25 and terminatin in avalve member 26, at tlie lower end t ereof. Conduit 25 rovides means of communication .between amber 21 anda reservoir 27, the conduit being provided withv a restricted opening or vent 28, for the purrom the main switch housing. As in the previous instance, a motor 29 for driving a centrifugal fluid impeller 30 is mounted with respect to reservoir 27 and when energized tends to force Aoil from the lower part of reservoir 27, through the inipeller discharge opening 3l, into a valve chamber 32 and upwardly through conduit 25 into chamber 21, in the eventthat valve 26 is open. An atmospheric vent 33 is adapted to maintain the interior of reservoir 27 and the interior of the switch housing at atmospheric pressure.

Motor 29 is adapted to be energized from a suitable source of power 34-35, through lead conductor 36 and a conductor 37 having4 interposed therein a control switch responsive to variations in the oil level within the main switch housing. In the present instance the control switch comprises a floatchamber 38 in communication with the main oil body below its normal levelthrou'h conduit 39, and provided with a float member 40 carrying a pair of vcontacts 41 and 42 adapted to be bridged by contacts 43 and 44. Variation of oil level within housing l accordingly produces a corresponding variation of thelevel within float chamber 38 with attendant rise and fall of float 40. Contacts 41 and 42 are maintained in alignment with contacts 43 and 44 through the guiding action of the insulating bushings 45 and 46. Upon an increase in height of the oil level, float 40 acts to separate the contacts 41 and 42 fromI the bridginoP elements to interrupt the motor circuit and thereby stop the fluid impeller, and vice versa, lowering of the oil level serves to bring float 40 and its associated contacts into .engagement with the bridging structure to complete the motor circuit and cause actuation of the fluid impeller.

The opening 22, which is disposed at the normal oil level, permits overow into chamber 21, and from there into reservoir 27 upon increase in volume of the oil due to increase in temperature. At the normal oil level, iloat 40 maintains the motor circuit open so that the fluid` impeller is idle. Assuming lfurther that the oil volume continues to increase, the excess oil will slowly flow by way of chainber 21, conduit 25 .into reservoir 27, thereby reventing rise in the oil level above vent 22. pon lowering of the oil level below vent 22, float 40 descends to complete the motor circuit and to start operation of impeller 30.

. In this event oil will flow from reservoir 27 upwardly through conduit 25, which was formerlythe discharge conduit, into chamber 21, and through vent 22 into the switch housing.

Impeller 30 continues to replenish the main oil body until its level has again been restored to approximately the level of vent 22, at which time float 40 will have broken the motor circuit. In the event that the float-operated control switch should 'fail for any Ysaid reservoir reason to interrupt the motor circuit, the increase in oil level due to continued energizetion of impeller 30, causes the float operated valve 26 to rise vertically and close to prevent further discharge through conduit 25. For the purpose of obtaining auxiliary or alternate control of the motor, pressure operated means may obviously be associated with the valve chamber 30 so that the increase in pressure therein due to closure of valve 26 may be ei'ective to actuate anl alarm, or even to interrupt the motor circuit itself.

The oil level in the present modification is likewise regulated near its normal level, thereby preventing agitation of the main oil body and the stirring up of sludge or other sediment.

It shall be understood that various changes may be made in the systems herein described and illustrated without departing from the spirit of my invention, for example, a plu` rality of circuit breakers may be connected to a single reservoir and fluid impeller, and a uniform oil level for all of the circuit breakers may be accordingly maintained.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. Electrical apparatus including an enclosed oil-containing receptacle and current carrying structure immersed in said oil, and means maintaining a predetermined level of said oil comprising a reservoir containing cil, the capacity of said reservoir being at least equal in volume to the diierence be- 'tween the maximum and minimum volumes oiE the oil normally contained within said receptacle, a conduit in communication with said receptacleat said predetermined level for discharging oil into said reservoir and l s 1 I n iiuid actuating means for rorcing oil from into said receptacle at a point adiacent said level whereby agitation of the oil body is precluded.

2n The combination with an oil circuit i breaker comprising an enclosed oil-containing receptacle, and contact structure im merscd in said oil, the level of sai-d oil normally spaced la predetermined distance' from the 4top of said receptacle, of an overiiow conduit communicating with said receptacle at said normal oil level, a reservoir into which said conduit may'discharge upon increase in volume of the oil within said receptacle, and iiuid actuating means adapt-ed to discharge oil from saidreservoir into said receptacle at a point adjacent said level in response to decrease in volume of the oil below its normal level. i

3. The combination with an oil circuit breaker comprising an enclosed oil-containing receptacle and contact structure immersed in said oil, the level of said oil normallyy spaced a predetermineddistance from the top ofsaid receptacle,fof a conduit communicating with said receptacle at said norllt? l mal oil level, said conduit having a restricted ing receptacle, contact structure immersed in `Huid actuating means for causing said oil, of means for maintaining'a normal level of oil below a redetermined distance from the top of sai receptacle comprising a discharve conduit disposed at the normal level of the oil, a reservoir into which said conduit may discharge, fluid actuating means adapted to discharge oil from the reservoirv into said receptacle by way of said conduit, a fluid actuated valve closing said conduit upon increase of the oil level above its ynormal level, and iuid actuated means'controlling energization of said actuating means in res onse to variations in said oil level.

5. he combination with an oil circuit breaker, comprising an enclosed oil-containing receptacle, and contact structure immersed in said oil, of means for maintainingy a predetermined level of oil within said receptacle, comprising a conduit disposed at the normal level ofthe oil, a reservoir with respect to which said conduit is in communication, centrifugal fluid impeller means adapted to discharge oil from the reservoir into said receptacle'b way of said conduit, motive means for sai im eller, ,and a'oat operated switch -for contro ling energization of said motive means in response to variations in said oil level.

6. Circuit interrupting apparatus includoil-containing receptacle and contact structure immersed in said oil, and means for maintaining a normal level of said oil at a predetermined distance from. the top of said receptacle notwithstanding increase or decrease in volume of the oil comprising a conduit in communication with said receptacle at said normal level for discharging oil in response to increase in volume of the oil, and new of oil into said receptacle adjacent said normal level for com ensating for decrease in` volume of the oi v 7. Circuit interrupting apparatus including an oil circuit breaker having an enclosed oilcontaining receptacle and contact structure immersedr in said oil, and means for maintaining anormal level of said oil notwithstanding increase or decrease in volume thereof comprisinga reservoir containin oil, the capacity of said reservoir being at east `equal involume to the dierence between the ing'an oil circuit breaker having an enclosed jacent sa' l normal level whereby agitation of the oil a preciably below said normal level is preclu ed.

8. Circuit interrupting apparatus includin an oil circuit breaker liavingan enclosed oi -containing receptacle and contact structure immersed in said oil, and means for maintaining a normal-level of said oil notwithstanding increase or decrease in volume thereof comprising an overflow conduit inl communication with said receptacle adjacent said normal oil level, a reservoir into whichA said conduit may discharge upon increase in volume of the oil, the' capacity of said reservoir being at least equal in volume to the diierence between the maximum and minimum volumes ofthe oil, and Huid-actuating means includin a second conduit for forcing oil from said reservoir into said receptacle at a point adjacent said normal level thereby compensating for decrease in volume of said oil'.'

9. The combination with a tank partially filled with oil and electrical apparatus iinmersed in said oil. of Ameans maintaining a predetermined. oillevel comprisin a conduit in communication with said tan at said level,l a reservoir in communication with the other-end of said conduit, the'oil discharging through said conduit into said reservoir upon expansion of the oil above said level, and fluid actuating means for forcing oil from said reservoir through said conduit and into said tank upon recession of said oil below said level.y

10. The combination with a tank partially filled with -oil and electrical apparatus immersed in said oil, of means maintaining a redetermined oil level comprising a conduit in communication with said `tank at said level, a reservoir in communication with the other end of said conduit, said conduit discharging oil from said tank into said reservoir when said level is exceeded, duid actuated means for forcing oil from said reservoir through said conduit and into said tank when the oil recedes from said level, and a Boat operated valve closing 'said conduit when said level is exceeded.

In witness whereof, l have hereto set myl l JOHN D. HLLIARD. 

